Experimental intramammary infection of ewes with Staphylococcus aureus subsp anaerobius

The susceptibility of the ovine mammary gland to experimental infection with Staphylococcus aureus subsp anaerobius was studied in five lactating Churra ewes. The left mammary gland of each ewe was inoculated with bacteria while the right halves remained untreated and served as a control. A rapid cellular response was elicited in all inoculated glands. The reaction of inoculated mammary glands varied from that of clinical mastitis (ewes C and D) to subclinical mastitis (ewes B and E) or merely to a transient increase of somatic cell counts (ewe A). S aureus subsp anaerobius is less pathogenic for ewes by the intramammary route than S aureus since doses of about 10(8) bacteria caused clinical mastitis in only two of the inoculated animals.

Determination of patulin by reversed-phase high-performance liquid chromatography with extraction by diphasic dialysis

A simple and economical method has been developed for the determination of patulin in apple juice. The sample is extracted with ethyl acetate in a diphasic dialysis system, and the extract is cleaned up by elution from a Sep-Pak cartridge. Patulin is detected and determined by reversed-phase high-performance liquid chromatography using a Novapak C18 column and an ultraviolet detector. The lower detection limit is 1 microgram l-1 and the recovery is 85% at the 20 micrograms l-1 level.

Evaluation of complement activity by an enzyme immunoassay

An ELISA-type assay useful for the evaluation of the complement activity in serum is described. Aggregated pooled human IgG (IgGn) prepared so as to exclude large and small aggregates, to resemble soluble circulating immune complexes, was used to coat polystyrene microwells to serve as initiator of complement activation. Fresh serum, at different dilutions, as the source of the complement to be evaluated was added and the plate incubated 90 min at 37 degrees C. Then, a peroxidase-labeled antihuman C3c antibody was added to react with the bound C fragments. This was followed by 2,2'-azino-di-3-ethyl benzothiazoline sulfonic acid (ABTS), as the color reagent used for detection of the enzyme activity. In this system, theoretically, the levels of activating and regulatory complement components are evaluated up to the level of C3 splitting. The assay was applied in healthy volunteers to set normal values and in 15 patients suffering from systemic lupus erythematosus making possible the differentiation of those with normal and low complement levels.

Applicability of an immunoblot technique combined with a semiautomated electrophoresis system for detection of staphylococcal enterotoxins in food extracts

We studied the usefulness of an immunoblot technique for the detection of staphylococcal enterotoxins (SEs) in strains and food extracts. Food samples (milk, yogurt, hot dog sausage, cheese, and mayonnaise) were artificially contaminated with SEA through SEE. Protein A did not interfere with the results; it appeared on electrophoresis gels as bands with molecular weights higher than those of the SEs. Other food proteins were not revealed by the technique. The immunoblot technique proved to be fast, specific, and sensitive for the detection of SEs in foods.

Murine monoclonal antibodies against staphylococcal enterotoxin B: production and characterization

A group of 14 monoclonal antibodies (mAbs) to staphylococcal enterotoxin B (SEB) were obtained by fusion of Sp2/O myeloma cells with spleen cells from female BALB/c mice immunized with commercial SEB. The antibodies belonged to IgG1 and IgG2b subclasses. We evaluated the anti-SEB titres, competition assays and sensitivity of detection by indirect ELISA. Reactivity and cross-reactivity were also studied by indirect ELISA and confirmed by immunoblotting. All the mAbs reacted with SEB and with a second band which had a different electrophoretic mobility and probably represents an aggregate of SEB or SEB bound to membranes. Three mAbs reacted only with SEB and the rest showed cross-reactions with SEC1. No reactions were observed against any other serovar (SEA, SED and SEE) or other proteins.

Polyclonal antibodies against Staphylococcus aureus ATCC 12600 catalase do not recognize any protein in cellular extracts from S. aureus subsp. anaerobius

Rabbits were immunized with electrophoretically pure catalase from Staphylococcus aureus ATCC 12 600. The antiserum was used to study whether S. aureus subsp. anaerobius was able to synthesize the apoprotein of catalase. Proteins were separated on polyacrylamide gels (SDS-PAGE) and transferred to nitrocellulose membranes and were detected by immunoblotting. No protein reacting with the purified immunoglobulins against S. aureus ATCC 12,600 catalase could be detected in crude and partially purified cellular extracts from S. aureus subsp. anaerobius or its aerotolerant mutants.

Detection of enterotoxins and TSST-1 secreted by Staphylococcus aureus isolated from ruminant mastitis. Comparison of ELISA and immunoblot

The production of staphylococcal enterotoxins (SE) and toxic shock syndrome toxin-1 (TSST-1) was studied in 81 strains of Staphylococcus aureus isolated from cases of mastitis in cattle, goats and sheep. SE and TSST-1 were detected by two techniques: ELISA double antibody sandwich, and an immunoblot technique combined with a semiautomated electrophoresis system. More Staph. aureus strains isolated from sheep produced enterotoxins than those from goats and cattle. SEC was the predominant type in all isolates from these animal species. The highest proportion of strains producing TSST-1 were obtained from sheep, twice as many as those from goats or cows. The two techniques gave similar results, as all the strains positive by immunoblot were also positive by ELISA, and only three were positive by ELISA but negative by immunoblot.

Biliary excretion as possible origin of Listeria monocytogenes in fecal carriers

The presence of Listeria monocytogenes in feces of animals has been related with ingestion of contaminated foods. In the study reported here, healthy mice inoculated SC with L monocytogenes excreted the organism in their feces, regardless of whether they developed clinical signs of infection. Listeria monocytogenes was isolated simultaneously from liver, feces, and bile of inoculated mice, which strongly suggested that the microorganism reached the gastrointestinal tract by biliary excretion.

Lack of growth of heat-shocked Staphylococcus aureus surviving cells in common media and enterotoxin release

The ratio of the different types of S. aureus surviving cells immediately after sub-lethal heat treatment (52 degrees C for 15 min) was studied. A high ratio of cells which are unable to form colonies even in a common medium such as TSA was observed. This fact has not been reported previously for common media through recovery after heat shock has been widely studied. After the treatment, staphylococcal protein A, but no enterotoxin, was seen to be released into the extracellular environment.

Growth of Staphylococcus aureus and synthesis of enterotoxin during ripening of experimental Manchego-type cheese

To study the possible presence of staphylococcal enterotoxins in Manchego-type cheese, milk was inoculated with the enterotoxigenic Staphylococcus aureus collection strains FRI-100, S6, FRI-137, and FRI-472 to a final concentration of 10,000 to 25,000 cfu/ml. Cheese was prepared following the industrial specifications and ripened for 60 d. Batches were prepared with 1 and .1% lactic acid culture and labeled with the abbreviated name of the strain and the concentration of lactic acid culture. Mean staphylococcal counts in .1% lactic bacteria cheeses were usually more than 1 log higher than the corresponding 1% ones. Staphylococcal counts declined markedly after d 35 to 42, and, by the end of ripening, they had disappeared from some cheeses. Enterotoxins were present in five of the cheeses, three prepared with .1% and two with 1% lactic bacteria. Enterotoxins detected were A and D, the enterotoxins most commonly associated with human intoxication. The maximum level of enterotoxin A detected in cheese with strain FRI-100 and with the .1% culture was 222 ng/100 g of cheese; in cheese FRI-100 with 1%, 111 ng/100 g; in cheese S6 with .1%, 769 ng/100 g; and in cheese S6 with 1%, 33 ng/100 g. Maximum level of enterotoxin D detected in cheese FRI-472 with .1% was 38 ng/100 g.

Detection of staphylococcal enterotoxin and toxic shock syndrome toxin-1 (TSST-1) by immunoblot combined with a semiautomated electrophoresis system

An immunoblot technique combined with a semi-automated electrophoresis system has been developed for the detection of staphylococcal enterotoxins and toxic shock syndrome toxin-1 (TSST-1). The advantages of this method over other detection techniques include speed, sensitivity (10 ng/ml) and specificity. The use of semiautomated electrophoresis permits the routine detection of staphylococcal enterotoxins and TSST-1.

Transformation of sterigmatocystin and O-methylsterigmatocystin by aflatoxigenic and nonaflatoxigenic field isolates of the Aspergillus flavus group

Transformation of sterigmatocystin and O-methylsterigmatocystin (two metabolic aflatoxin precursors) to aflatoxins by aflatoxigenic and nonaflatoxigenic field isolates of Aspergillus flavus was studied. The 24 nonaflatoxigenic isolates investigated failed to transform both precursors. Among the 8 aflatoxin-producing isolated used, 7 transformed both precursors whereas the remaining failed to transform both. According to these results, the usefulness of the measurement of enzymatic activities related to aflatoxin production in understanding the true status of conflictive field isolates is discussed.

Fructose-induced fluorescence generation of reductively methylated glycated bovine serum albumin: evidence for nonenzymatic glycation of Amadori adducts

In vitro glycation of bovine serum albumin by fructose (fructation) induces fluorescence generation about 10-times faster than glucose (G. Suárez et al. (1989) J. Biol. Chem. 264, 3674-3679). In order to gain further insight into possible mechanisms that would explain this difference, the protein was glycated with either glucose or fructose and then reincubated in the absence of sugars. In contrast to the previous findings, albumin that had been glycated with glucose generated fluorescence at a higher rate during the sugar-free incubation. However, when partially glycated BSA was reincubated with sugars under conditions where de novo glycation was prevented by reductive methylation of amino groups fructose induced fluorescence to a much larger extent than glucose. These results are consistent with the notion of covalent addition of sugars to Amadori groups, the earliest stable products of the Maillard reaction. A chemical pathway is proposed where pyrrolic structures result from the double sugar adducts by aldol condensation and dehydration. These structures might be precursors of fluorophores.

Overlay technique for direct detection and identification of haemolytic Listeria on selective plating medium. Comparison of five media

An overlay technique is proposed for the identification and counting of haemolytic Listeria colonies directly on selective plating media. The technique was applied to different Listeria-selective plating media. In pure culture studies with collection strains, the overlay technique was more efficient and reliable for detection haemolytic Listeria species compared with the incorporation of blood into the agar. The efficacy of the overlay technique for the direct detection of haemolytic colonies of Listeria from raw milk samples was related to agar selectivity. The best results were obtained with Listeria-selective agar medium modified (LSAMM). Catalase assay, together with reactions for aesculin and tellurite, were useful and reliable criteria for the identification of Listeria. All colonies on LSAMM which were positive for catalase, tellurite and aesculin while those displaying typical haemolysis corresponded in most cases to L. monocytogenes.

Influence of Temperature of Incubation on Staphylococcus aureus Growth and Enterotoxin Production in Homemade Mayonnaise

Homemade mayonnaise, in which pH had been adjusted to a range between 5.0 and 5.8 by the addition of vinegar, was inoculated with eight Staphylococcus aureus strains known to be enterotoxigenic. They were incubated for a maximum of 7 days at 22, 28, 37, and 44°C. Periodically, staphylococcal growth and pH were determined. Mayonnaise samples were examined on d 7 for the presence of enterotoxins A, B, C, and D. Staphylococcal growth was higher at 22°C (average log₁₀ 7.21 cfu/g), than at the other temperatures tested (log₁₀ 7.15, 6.77, and 5.93 cfu/g, respectively for 28, 37, and 44°C), suggesting a better growth in mayonnaise at low room temperature. Enterotoxin synthesis took place mainly at 28°C, as 33.3% of the total enterotoxins produced were detected at this temperature. However, some strains synthesized high amounts of enterotoxin even at 22°C.

[Heart hydatidosis diagnoses with bidimensional echocardiography]

A case of calcificated intramyocardiac hydatid cyst is presented. The initial diagnosis was coronary artery disease and the onset was chest pain and typical abnormalities of the electrocardiogram. The diagnosis of hydatid disease was suspected from chest roentgenogram and confirmed by two-dimensional echocardiography and left ventriculography. Coronary arteriography was normal and surgical treatment successfully carried out.

Growth of Staphylococcus aureus and synthesis of enterotoxins in home-made yoghurt

Staphylococcus aureus strains FRI-100, S6, FRI-137 and FRI 472 were inoculated into milk to study growth and enterotoxin production in home-made yogurts. The yogurt used as starter was progressively weakened by successive inoculations (up to four) in milk to prepare other yogurts in order to study the ability of yogurt microflora to inhibit staphylococci. After elaboration, yogurts were stored at 4 degrees C, 22 degrees C, and 37 degrees C for a maximum of 21 days. Periodically, staphylococcal counts, pH and the production of enterotoxins A, B, C, and D were determined. Enterotoxins were only detected in the last batch. It was concluded that the inhibitory effect of the starter culture is not only due to the decrease of pH, but also to other factors.

Production of enterotoxin A by supposedly nonenterotoxigenic Staphylococcus aureus strains

The production of staphylococcal enterotoxins A (SEA) and B (SEB) was studied by inoculating six well-defined staphylococcal collection strains into cow's, goat's, or sheep's milk (individually or as a 50% mixture of cow's + goat's or cow's + sheep's), into brain heart infusion, and into a medium generally used to enhance the synthesis of enterotoxins (3+3 medium). Four of the strains used are considered to be SEB producers, another is considered an SEA producer, and the remaining strain is nonenterotoxigenic but produces large quantities of staphylococcal protein A. Staphylococcal protein A masked the results in most cases. Only one strain secreted exclusively SEB, while the other three SEB producers synthesized SEA in different amounts. We conclude that enterotoxin production depends on the natural substrate and may differ from the results obtained when the strain is grown on cellophane over agar to determine its toxigenicity.

Nonenzymatic glycation of bovine serum albumin by fructose (fructation). Comparison with the Maillard reaction initiated by glucose

Nonenzymatic glycation by glucose (glucation) was compared with glycation by fructose (fructation). The rate and extent of protein-bound fluorescence generation upon fructation was about 10 times that upon glucation. In contrast, nonenzymatically glucated bovine serum albumin (BSA) released about twice as much formaldehyde upon periodate oxidation as did nonenzymatically fructated BSA. However, the rate of blocking of amino groups was similar in both proteins. Periodate oxidation of borohydride-reduced glycated BSA led to regeneration of amino groups with preservation of fluorescence. From the ratio between the decrease in formaldehyde-releasing ability and the regenerated amino groups, formaldehyde molar yields of 0.47 and 0.8 were computed for fructose- and glucose-derived Amadori groups, respectively. This is consistent with participation of both carbon 1 and carbon 3 in the Amadori rearrangement from fructose. The formaldehyde releasing ability of nonenzymatically fructated BSA attains asymptotic maximum values earlier than that of nonenzymatically glucated BSA. Thus, the higher rate of fluorescence generation in nonenzymatically fructated BSA could be explained by a faster conversion of its Amadori groups. Since fluorescence generation through the Maillard reaction has been correlated with long term complications of diabetes mellitus, the participation of nonenzymatic fructation in this pathological state deserves further exploration. This is especially relevant in tissues where fructose levels increase in diabetes as a result of the operation of the sorbitol pathway.

Assessment of different selective agar media for enumeration and isolation of Listeria from dairy products

Different selective agar media were compared for the recovery and isolation of five species of Listeria from raw milk and cheese. The selective media examined were Beerens medium, MacBride medium and that described by Dominguez et al. (1984) with 6 mg/l acriflavine, listeria selective agar medium (LSAM), and LSAM with 12 mg/l acriflavine (LSAM X 2A); a non-selective yeast glucose Lemco agar was included for comparison. When the difference between listeria and the natural microflora of raw milk and cheese was 10(2) cfu/ml, listeria could be isolated by direct plating on all media tested. When it was lower than 10(3)-10(4) cfu/ml, listeria were isolated by direct plating only on LSAM and LSAM X 2A. When the difference was greater than 10(4) cfu/ml, a previous enrichment was necessary to isolate them. LSAM and LSAM X 2A media performed better than the other media tested for isolating listeria by direct plating and improved their isolation from dairy products. This superior performance was evaluated by the ability of these media to support colony formation of different species of Listeria tested, the easy recognition of these colonies from those formed by other microorganisms and by their capacity to inhibit the natural microflora of these foods.

Administration of an aldose reductase inhibitor induces a decrease of collagen fluorescence in diabetic rats

As a consequence of an increased flux through the sorbitol pathway fructose levels rise in various tissues in diabetes. Also, in vitro nonenzymatic fructosylation of protein induces the generation of fluorescence at a rate 10 times greater than glucosylation. The administration of sorbinil, an aldose reductase inhibitor known to lower tissue fructose concentration, to experimental diabetic rats led to a decrease in the fluorescence related to advanced Maillard products in their skin collagen. This effect is consistent with the in vivo occurrence of nonenzymatic fructosylation of collagen. A potential pathogenetic role for this posttranslational modification in diabetic complications should be considered.

Presence of aflatoxin M1 in commercial ultra-high-temperature-treated milk

Forty-seven samples of commercial ultra-high-temperature-treated milk from a dairy facility in the northwest part of Spain were analyzed for the presence of aflatoxin M1. A total of 14 samples (29.8%) were positive for aflatoxin M1 (4 in May, 3 in November, 3 in December, 1 in January, 1 in April, 1 in July, and 1 in August), 29 (61.7%) were negative, and 4 (8.5%) were doubtful, i.e., they showed trace quantities of aflatoxin M1. The range of aflatoxin M1 content was 0.02 to 0.1 ng/ml.

Experimental aflatoxin production in home-made yoghurt

Fungal growth and aflatoxin production by an aflatoxigenic strain during the manufacture of yoghurt are described. This completes previous studies which show that yoghurt may be a good substrate for aflatoxin production. Two factors were of special interest: (a) the temperature of the elaboration process (45 degrees C) and (b) the effect of lactic bacteria. Either during the elaboration of yoghurt or during its cooling from 45 degrees C to 4 degrees C, the necessary conditions required to start fungal growth are given; these are adequate enough for the synthesis of small quantities of aflatoxins. However our results do not clearly show that lactic bacteria have an influence on fungal growth and aflatoxin production.

Experimental aflatoxin production in commercial yoghurt

The production of aflatoxins in commercial yoghurt inoculated with Aspergillus parasiticus NRRL 2999 was studied, using different incubation conditions. In all of the experiments, the level of aflatoxins was higher at 28 degrees C than at 15 degrees C and higher in a "damaged" container than in an "intact" container (related to microaerophilic conditions). No fungal growth or aflatoxin production was seen at 10 degrees C. Both fungal growth and aflatoxin concentration vary throughout the incubation period instead of progressively increasing. The ratio of aflatoxin B and G (B:G) at 28 degrees C was almost 1:1, but generally more aflatoxin G was detected at 15 degrees C. The distribution in mycelium/substrate was approximately 1:1 at both 28 degrees C and 15 degrees C.

Experimental aflatoxin production in Manchego-type cheese

Manchego-type cheese, a typical Spanish cheese, was inoculated in various ways with an aflatoxigenic organism, Aspergillus parasiticus NRRL 2999, to study the production of aflatoxin. When the original milk was contaminated with a spore suspension, aflatoxin was not detected in paraffin-covered cheeses although it was present in the top layer of non-paraffin-covered cheeses after ripening at 15 degrees C for 60 d. When the cheese surface was inoculated, no aflatoxins were detected in paraffin-covered cheeses after ripening for 60 d although they were found when the cheeses were ripened for 30 d. In non-paraffin-covered cheeses aflatoxins were detected only in the top layer and in the second 10 mm layer when cheeses were incubated after the normal ripening at 28 degrees C for 30 d. When the centre of the cheese was inoculated, no aflatoxins were detected although Aspergillus grew slightly along the inoculation area. When cheese portions were inoculated, fungal growth was evident after incubation at 28 degrees and 15 degrees C for 6 d but there was no growth at 10 degrees C after 50 d. At 28 degrees C aflatoxins were detected at a concentration of 132 micrograms/g after 13 d, the highest level obtained. In cheese paste at 28 degrees and 15 degrees C, growth was intense, but the level of aflatoxins detected was lower than in cheese portions. At 10 degrees C the growth was heavy, but aflatoxins were not detected.

Effect of ultraviolet light irradiation on viability and aflatoxin production by Aspergillus parasiticus

The effect of ultraviolet light irradiation (254 nm) on both the viability and the aflatoxin-producing ability of the fungus Aspergillus parasiticus NRRL 2999, a good aflatoxin-producing strain, was studied. This strain showed noticeable resistance and irradiation for more than 10 min was necessary to reduce survival to under 10%, while the white mutants were more susceptible (5 min of irradiation reduced survival to under 1%). Induction of mutants with complete loss of aflatoxigenicity was rare and only 3 of the 1463 survivors tested were aflatoxinless.

[Relation between meteorological conditions and the atmospheric microflora of the city of Barcelona]

This work deals with a study of the changes observed throughout the four seasons of the year concerning the number of fungi which can be found in the atmosphere of Barcelona. The results obtained will bring us to the conclusion that during the autumn and winter months the number of conidia per m3 is greater than in spring and summer. This observation would confirm the fact that generally speaking in autumn and winter, temperature decreases and humidity increases, while the opposite occurs in spring and summer. These phenomena would be directly related to our findings where we have established that an increase in temperature implies a reduction on the airborne fungi, while the remaining climatic factors taken into account would indicate an increase in the total fungal population. The same relation - phenomena were observed for the strains of the genus Cladosporium, Penicillium, Aureobasidium, Aspergillus and Alternaria, though with some modifications in the three later.

Plasma fibrinogen concentration in ABO-hemolytic disease of the newborn

Plasma fibrinogen and total serum proteins were measured in infants affected by ABO-hemolytic disease and in normal infants' cord blood and blood taken 48 h after birth. The average plasma fibrinogen concentrations in the blood of infants with ABO-hemolytic disease was 447.36 mg/dl as compared with 267.09 mg/dl (p less than 0.005) in cord blood and 313.82 mg/dl (p less than 0.005) in blood samples taken 48 h after birth. A simple 'autoagglutination' test is found to be helpful when establishing the diagnosis of ABO-hemolytic disease.

[Acute glomerulonephritis in children: long-term prognosis]

Sixty-five children were studied for over five years following an acute glomerulonephritis episode. Proteinuria was detected in 15 but in one, it was massive proteinuria with edema and low renal function. The other 14 children were asymptomatic and proteinuria was close to or below 0.5 gms/24hs. Only one out of 10 renal biopsies was normal. Focal mesangial proliferation was described in 9. Such renal lesion was considered as residual rather than active. From these results it is concluded that the prognosis of acute glomerulonephritis in children is good in 98% of cases.

Protein synthesis by synaptosomes from rat brain: the effect of centrifugal forces

1. Synaptosomal protein synthesis has been found to differ depending on whether synaptosomes are recovered from the sucrose gradients by centrifuging at 20,000 g or at 150,000 g. 2. The fraction obtained at 20,000 g incorporated 60% more amino acid into proteins after 30 min of incubation than the one obtained in the same period of time at 150,000 g. 3. The respiratory capacity of synaptosomes obtained at 20,000 g in the presence or absence of glucose as substrate, is also better preserved than that of those obtained at 150,000 g. 4. It is shown that the yield, enzymic content, and nucleic acid composition is the same in both fractions. 5. These results cannot be explained by the presence of inhibitory factors in the 150,000 g fraction or by the presence of better preserved free mitochondria in the 20,000 g fraction. 6. Our findings are best explained by postulating that the synaptosomal metabolic activity is damaged when synaptosomes are pelleted at too high a speed.